1. Field of the Invention
This invention relates to a waveform data processing system and a method of waveform data processing for electronic musical instruments and, more particularly, to control of writing and reading data of musical tone waveforms in electronic musical instruments.
2. Description of the Related Art
In a prior art tone generator for an electronic musical instrument, sampled musical tone waveform data is stored in a waveform memory, and is read out when a key-"on" event signal is supplied. The key-"on" event signal is also supplied to an envelope generator for calculating envelope waveform data. The envelope waveform data is used to multiply the musical tone waveform data for D-A (digital-to-analog) conversion, the converted data being output. The key-"on" event signal may correspond to an "on" event concerning a keyboard key or correspond to automatic performance information.
In the waveform memory, musical tone waveform data of sinusoidal waves, triangular waves, rectangular waves, etc., is stored for one wavelength portion, and it is read out repeatedly at a rate corresponding to the tone pitch. In some tone generators, for more closely approximating sounds of actual musical instruments, musical tone waveform data of a plurality of gradually changing waveforms or an attack waveforms of musical tones and portions of waveforms subsequent from the attack is stored in a waveform memory.
However, the musical tone waveform data stored in the waveform memory is fixed and cannot be altered. Therefore, tones sounded in performance have fixed tone color and poor variations.
To obtain sounding of tones having a variety of tone colors, it is necessary to store a great number of different kinds of musical tone waveform data, and doing so requires an enormous waveform memory capacity and a complicated process for selecting and accessing stored data.
The present invention seeks to solve the above problems, and its object is to provide a waveform data processing system, which permits sounding tones of a great variety of tone colors without the need to increase the storage capacity of a waveform memory means.
With the prior art tone generator, there are cases when waveform data stored in the waveform memory is not desired by the operator, that is, waveform data corresponding to musical tones desired to be sounded may fail to be stored. Particularly, when waveform data corresponding to tones desired to be sounded fail to be stored in the case of automatic performance, the performance may fail to be executed or may be interrupted.
Another object of the invention is to provide a waveform data processing system for an electronic musical instrument, which permits necessary musical tone waveform data to be automatically transferred and stored.